Electron spin resonance on (100)Si/SiOx/ZrO2 and (100)Si/Al2O3/ZrO2 stacks with nm-thin dielectric layers reveals the Si dangling-bond-type centers Pb0, Pb1 as prominent defects at the (100)Si/dielectric interface. This Pb0, Pb1 fingerprint indicates that, while gratifying for the Si/SiOx/ZrO2 case, the as-deposited (100)Si/Al2O3 interface is basically Si/SiO2-like. The interfaces are in an enhanced (unrelaxed) stress state, characteristic of low-temperature Si/SiO2 growth. Based on the Pb0, Pb1 criterion, standard thermal Si/SiO2 interface properties may be approached by appropriate annealing (≥ 650 °C) in vacuum in the case of Si/SiOx/ZrO2. Yet, O2 ambient is required for Si/Al2O3, indicating that the initial abruptness of the interface prevents thermal adaptation to occur until an additional SiOx interlayer grows. A minimal SiOx interlayer thickness (≳0.5 nm) appears requisite. © 2002 American Institute of Physics.